WO2020195405A1 - Low thermal expansion alloy having excellent low temperature stability and method for producing same - Google Patents

Low thermal expansion alloy having excellent low temperature stability and method for producing same Download PDF

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WO2020195405A1
WO2020195405A1 PCT/JP2020/006778 JP2020006778W WO2020195405A1 WO 2020195405 A1 WO2020195405 A1 WO 2020195405A1 JP 2020006778 W JP2020006778 W JP 2020006778W WO 2020195405 A1 WO2020195405 A1 WO 2020195405A1
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thermal expansion
alloy
less
low thermal
ppm
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PCT/JP2020/006778
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French (fr)
Japanese (ja)
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半田　卓雄
志民 劉
大山　伸幸
鷲尾　勝
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日本鋳造株式会社
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Priority to US17/435,780 priority Critical patent/US11840752B2/en
Priority to JP2020528976A priority patent/JP6754027B1/en
Priority to CN202080006969.3A priority patent/CN113195763B/en
Priority to EP20779916.4A priority patent/EP3950998B1/en
Priority to KR1020217020195A priority patent/KR102345951B1/en
Publication of WO2020195405A1 publication Critical patent/WO2020195405A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing

Definitions

  • the present invention relates to a low thermal expansion alloy having excellent low temperature stability and a method for producing the same.
  • the low thermal expansion alloy material is applied for the purpose of suppressing thermal deformation due to temperature changes of precision equipment in various advanced fields. If the coefficient of thermal expansion is zero, thermal deformation does not occur due to temperature changes, making it an ideal material.
  • Some parts such as aerospace equipment and measuring equipment operate in the low temperature range, and may be used at -100 ° C or lower. Even in such a low temperature range, there is no sudden change in the coefficient of thermal expansion due to structural changes, and the coefficient of thermal expansion between 100 ° C and -70 ° C can be regarded as virtually zero expansion at 0 ⁇ 0.2 ppm / ° C.
  • An alloy material within the range of is desired.
  • SI Super Invar
  • Fe-Ni-Co-based low thermal expansion alloys typified by Super Invar (SI) are industrially used as low thermal expansion materials.
  • SI is a low expansion of Fe-36% Ni alloy (Invar) having a coefficient of thermal expansion near room temperature of 1 to 2 ppm / ° C by replacing a part of Ni with Co.
  • Invar has an Ms point of -196 ° C or lower, and the structure does not change even at -196 ° C or lower and maintains low thermal expansion. Therefore, the exposure temperature of Invar is lower than -100 ° C for aerospace equipment and measuring equipment. It can also be applied to.
  • the coefficient of thermal expansion is 1 to 2 ppm / ° C., which is larger than SI, and there is a large gap from zero expansion. Therefore, the effect of suppressing thermal deformation is insufficient, and there is a problem that it cannot meet high demands. (Paragraph 0024 of Patent Document 1).
  • the dendrite secondary arm spacing is set to 5 ⁇ m or less by irradiating an alloy powder having a specific composition with a laser or an electron beam to melt, rapidly solidify, and laminate, to 0.5 ppm / ° C or less. It has been proposed to achieve both the coefficient of thermal expansion of the above and the low temperature stability that could not be obtained by SI.
  • SI forms a martensite structure at a low temperature such as -100 ° C, and the coefficient of thermal expansion increases sharply.
  • Invar has a coefficient of thermal expansion of 1 to 2 ppm / ° C and has an effect of suppressing thermal deformation. Insufficient.
  • the low thermal expansion alloy of Patent Document 2 cannot be said to stably exhibit zero expansion, and cannot obtain the same low temperature stability as the Invar alloy. Therefore, a material that can realize zero expansion between 100 ° C. and ⁇ 70 ° C. and can obtain low temperature stability comparable to that of Invar alloy has not yet been obtained.
  • the average coefficient of thermal expansion between 100 ° C. and ⁇ 70 ° C. is 0 ⁇ 0.2 ppm / ° C., which can be regarded as zero expansion, and a low thermal expansion alloy having the same low temperature stability as an Invar alloy can be obtained. And its manufacturing method.
  • the low thermal expansion alloy material having the composition according to (1) or (2) above is melted and solidified by a laser or an electron beam to form a laminate, and the average coefficient of thermal expansion at 100 to ⁇ 70 ° C. is 0.
  • a method for producing a low thermal expansion alloy which comprises producing a low thermal expansion alloy in the range of ⁇ 0.2 ppm / ° C. and having an Ms point of -196 ° C. or lower.
  • the average coefficient of thermal expansion between 100 ° C. and ⁇ 70 ° C. is 0 ⁇ 0.2 ppm / ° C., which can be regarded as zero expansion, and low heat stability comparable to that of Invar alloy can be obtained.
  • Expansion alloys and methods for producing them are provided.
  • the largest factor that determines the coefficient of thermal expansion of Fe-Ni-Co-based low thermal expansion alloys is the Co content, but the addition of Co relatively reduces the Ni content and destabilizes austenite. , Ms rises.
  • the Ms point is around -40 ° C, so it cannot be applied at lower temperatures. Therefore, it is difficult to stably set the coefficient of thermal expansion to 0 ⁇ 0.2 ppm / ° C. in the temperature range from around room temperature to ⁇ 70 ° C. as long as Co is used for low thermal expansion.
  • the present inventors have investigated a low thermal expansion technique that does not involve an increase in the Ms point due to Co, which is found in conventional Fe-Ni-Co low thermal expansion alloys.
  • C, Si, and Mn are reduced, the microstructure is reduced, and the dendrite secondary arm spacing is set to 5 ⁇ m or less, so that the temperature is between 100 ° C. and ⁇ 70 ° C.
  • the coefficient of thermal expansion of the above is 0 ⁇ 0.2 ppm / ° C., which can be regarded as zero expansion, and low temperature stability comparable to that of Invar alloy can be obtained.
  • the present invention has been completed based on these findings.
  • the% representation of the components is mass%
  • ⁇ is the average coefficient of thermal expansion of 100 to ⁇ 70 ° C.
  • C 0.015% or less
  • C is an element that significantly increases ⁇ of the low thermal expansion alloy according to the present invention, and is preferably low. If C is contained in excess of 0.015%, ⁇ exceeds the range of 0 ⁇ 0.2 ppm / ° C depending on the content of other elements described later, so the C content is set to 0.015% or less.
  • Si 0.10% or less
  • Si is an element added for the purpose of reducing oxygen in the alloy.
  • Si is an element that remarkably increases ⁇ of the low thermal expansion alloy according to the present invention, and it is desirable that it is low. If the content exceeds 0.10%, the increase in ⁇ cannot be ignored as in C. Therefore, the Si content is set to 0.10% or less.
  • Mn 0.15% or less
  • Mn is an element effective for deoxidation like Si.
  • Mn is an element that significantly increases ⁇ in the low thermal expansion alloy according to the present invention, and is preferably low. If the content exceeds 0.15%, the increase in ⁇ cannot be ignored as in C. Therefore, the Mn content is set to 0.15% or less.
  • Ni 35.0 to 37.0%
  • Ni is an element that determines the basic ⁇ of an alloy. In order to set ⁇ in the range of 0 ⁇ 0.2 ppm / ° C, it is necessary to adjust it to the range described later according to the amount of Co. When Ni is less than 35.0% or more than 37.0%, it is difficult to set ⁇ in the range of 0 ⁇ 0.2 ppm / ° C. even by adjusting according to the amount of Co and the production conditions described later. Therefore, the Ni content is set in the range of 35.0 to 37.0%.
  • Co Less than 2.0% Co is an important element that determines ⁇ together with Ni, and is an element added to obtain a smaller ⁇ than when Ni alone is added. However, when Co is 2.0% or more, the amount of Ni obtained based on the relational expression between the amount of Ni and the amount of Co described later decreases, and austenite becomes unstable, so that the Ms point becomes higher than -196 ° C. Therefore, the Co content is set to less than 2.0%. 1.0% or less is preferable from the viewpoint of eliminating the need for the prescribed management and measures of the Safety and Health Law Specialization Regulations.
  • Ni + 0.8Co 35.0-37.0%
  • the Fe—Ni—Co alloy can obtain remarkable low thermal expansion property in the above-mentioned Ni amount and Co amount range and in a certain range of Ni equivalent (Nieq.) Expressed by Ni + 0.8 ⁇ Co. Even if the Ni equivalent is less than 35.0% or more than 37.0%, ⁇ does not fall within the range of 0 ⁇ 0.2 ppm / ° C. Therefore, the Ni equivalent of Ni + 0.8Co is set in the range of 35.0 to 37.0%.
  • C ⁇ 7 + Si ⁇ 1.5 + Mn ⁇ 0.40 In the Fe—Ni—Co alloy of the present invention, the amount of C, the amount of Si, and the amount of Mn are defined in the above ranges, and the value of the formula represented by C ⁇ 7 + Si ⁇ 1.5 + Mn is 0.40 or less. Therefore, a remarkable low thermal expansion property is obtained. Therefore, it is preferable to set C ⁇ 7 + Si ⁇ 1.5 + Mn ⁇ 0.40.
  • the balance other than C, Si, Mn, Ni and Co is Fe and unavoidable impurities.
  • [Coagulation tissue] ⁇ can be reduced by making the solidified structure finer. The reason is considered to be that the microsegregation of Ni is reduced by the miniaturization of the structure as described above.
  • the solidified structure is refined so that the dendrite secondary arm (DAS) spacing is 5 ⁇ m or less.
  • DAS dendrite secondary arm
  • the low thermal expansion alloy according to the present invention has a low Co content, a Ni content of 35% or more, and has a fine solidification structure as described above. Therefore, the Ms point is -196 ° C. or lower, which is about the same as that of the Invar alloy. Therefore, excellent low temperature stability comparable to that of Invar alloy can be obtained.
  • the low thermal expansion alloy material having the above composition is melted and solidified by a laser or an electron beam to form a laminated structure.
  • the low thermal expansion alloy material is melted and then rapidly cooled, so that the DAS interval can be made into a fine structure of 5 ⁇ m or less.
  • the microsegregation of Ni is reduced, and ⁇ can be set in the range of 0 ⁇ 0.2 ppm / ° C.
  • any method can be applied as long as the melting / solidifying conditions for obtaining a fine solidified structure having a DAS of 5 ⁇ m or less can be realized.
  • an alloy powder is prepared as an alloy material having a composition within the above range, melted and solidified by a laser or an electron beam, and laminated to form an alloy having a DAS interval of 5 ⁇ m or less. be able to.
  • the cooling rate at the time of solidification of the alloy is 3000 ° C./sec. With the above, a fine solidified structure having a DAS interval of 5 ⁇ m or less can be obtained. A laser or electron beam will satisfy this cooling rate.
  • the cooling rate is insufficient to reduce the DAS to 5 ⁇ m or less even by the die casting having the highest cooling rate, much less the alloy of the present invention.
  • a copper alloy type capable of casting such a high melting point iron-based alloy as shown in FIG. 5 below, it is impossible to reduce the DAS to 5 ⁇ m or less, and the desired characteristics are obtained. That is impossible.
  • the average coefficient of thermal expansion between 100 ° C. and ⁇ 70 ° C. is 0 ⁇ 0.2 ppm / ° C., which can be regarded as zero expansion, and low heat stability comparable to that of Invar alloy can be obtained.
  • An expansion alloy is obtained.
  • the low thermal expansion alloy according to the present invention can be applied to various precision equipment members operating in a low temperature region including the aerospace field, which has been restricted in application with the conventional low expansion alloy, and is highly applicable in the field. Greatly contributes to accuracy.
  • SI which is a Fe-Ni-Co-based low thermal expansion alloy
  • the low thermal expansion alloy according to the present invention has a low Co content of less than 2%, which can suppress an increase in material cost, and when the Co content is 1 mass% or less, only the Co content is indicated at the time of application. All that is required is that the prescribed management and measures of the Safety and Health Law Specialization Regulations are not required.
  • Samples were prepared by laminating the alloys of the chemical components and compositions shown in Table 1 and casting them into a pure copper mold.
  • the alloy having the chemical composition shown in Table 1 is melted in a high-frequency induction furnace, the molten metal is dropped using the atomizing apparatus shown in FIG. 1, and an inert gas (nitrogen gas in this example) is dropped from the nozzle. ) was sprayed to divide into droplets and rapidly solidify to obtain a spherical powder. Then, it was sifted to obtain a modeling powder having a particle size of 10 to 45 ⁇ m shown in FIG.
  • the modeling powder is laminated and modeled under the conditions of output 300 W, laser moving speed 1000 mm / sec, laser scanning pitch 0.1 mm, and powder layered thickness 0.04 mm, and a sample of ⁇ 10 ⁇ L100 is prepared. Made.
  • FIG. 3 shows the cooling rate of the sample estimated from the DAS measured by observing the microstructure of the sample of the present invention and the extrapolation line of the relationship between the DAS and the cooling rate described in Document 1 below.
  • the cooling rates of various molds obtained from the information of 2 to 4 are also shown.
  • R (DAS / 709) 1 / -0.386 ...
  • R Cooling rate (° C / min.)
  • DAS Dendrite secondary arm spacing ( ⁇ m)
  • Reference 1 “Cast Steel Production Technology” P378, Raw Material Center Reference 2: “Casting", Vol. 63 (1991) No. 11, P915 Reference 3: “Casting Engineering", Vol. 68 (1996) No. 12, P1076 Reference 4: “Shaping Material", Vol.54 (2013) No.1, P13
  • the sample was separated from the modeling base plate by a discharge wire cut, then machined into a thermal expansion test piece of ⁇ 6 x 50 mm, and used at 2 ° C / min with a laser interference type thermal expansion meter. The thermal expansion was measured while raising the temperature with, and ⁇ was obtained from the obtained thermal expansion curve.
  • the thermal expansion test piece was set in the thermal expansion meter, and liquid nitrogen was used at 3 ° C./min. The thermal expansion was measured while cooling with, and it was obtained from the temperature at which the thermal expansion curve changed abruptly.
  • the sample was immersed in liquid nitrogen for 15 minutes, and then the microstructure was observed to confirm the presence or absence of the martensite structure.
  • Example No. of the present invention in Table 1. 1 to 8 are those whose chemical composition and composition are within the range of the present invention and are manufactured by powder additive manufacturing, and all of them have an ⁇ of 0 ⁇ which is an average coefficient of thermal expansion between 100 and ⁇ 70 ° C. The range of 0.2 ppm / ° C. and the Ms point were -196 ° C. or lower.
  • No. 4 and No. No. 8 has a similar composition, but No. No. 4 has 7C + 1.5Si + Mn of 0.4 or less, and No. 8 is over 0.4. Comparing these, ⁇ was in the range of 0 ⁇ 0.2 ppm / ° C., but No. 7C + 1.5Si + Mn satisfied 0.4 or less. No. 4 is No. The value of ⁇ became smaller than 8.
  • FIG. 4 shows Example No. of the present invention. It is the optical micrograph of No. 7. From this optical micrograph, No. As a result of actually measuring the DAS of 7, it was 1.4 ⁇ m and 5 ⁇ m or less. Further, the value of the DAS, the cooling rate is 1.5 ⁇ 10 5 °C / sec. Estimated.
  • the alloy of the present invention has characteristics that can meet the strict requirements in the aerospace field.
  • No. of Comparative Example A Nos. 11 to 17 are No. 1 of the invention examples, respectively. It has the same chemical composition and composition as 1 to 7, but it is cast in a pure copper mold and has a DAS of more than 5 ⁇ m, which is outside the scope of the present invention.
  • FIG. 5 shows No. 5 of Comparative Example A. It is an optical microscope photograph of 17, and from this photograph, No. The actual measurement result of DAS when cast into 17 pure copper molds was 16 ⁇ m. Therefore, No. In all of 11 to 17, ⁇ was out of the range of 0 ⁇ 0.2 ppm / ° C.
  • Nos. 18 to 24 have chemical components and compositions outside the scope of the present invention, and are obtained by laminating molding and casting into a pure copper mold to prepare a sample.
  • No. In 18, C is No. In No. 19, Si is No. In No. 20, Mn is No. Since the Ni and Ni equivalents of No. 22 exceeded the upper limit, ⁇ was a value outside the range of 0 ⁇ 0.2 ppm / ° C. regardless of the production method.
  • ⁇ was a value outside the range of 0 ⁇ 0.2 ppm / ° C., and the Ms point was higher than -196 ° C. regardless of the production method.
  • Comparative Example B No. Reference numeral 24 denotes SI of the conventional alloy, and the Ms point was higher than -196 ° C. regardless of the production method.

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Abstract

Provided is a low thermal expansion alloy that contains, in mass%, not more than 0.015% of C, not more than 0.10% of Si, not more than 0.15% of Mn, 35.0-37.0% of Ni, and less than 2.0% of Co. Ni+0.8Co is 35.0-37.0%, and the remaining portion is Fe and unavoidable impurities. The low thermal expansion alloy has a solidification structure in which the secondary dendrite-arm spacing is 5 μm or less, has an average thermal expansion coefficient in a range of 0±0.2 ppm/°C at 100°C to -70°C, and has an Ms point of -196°C or less.

Description

低温安定性に優れる低熱膨張合金およびその製造方法Low thermal expansion alloy with excellent low temperature stability and its manufacturing method
　本発明は、低温安定性に優れる低熱膨張合金およびその製造方法に関する。 The present invention relates to a low thermal expansion alloy having excellent low temperature stability and a method for producing the same.
　低熱膨張合金材料は、各種先端分野の精密装置の温度変化に伴う熱変形を抑える目的で適用される。熱膨張係数がゼロであれば温度変化に伴う熱変形が発生しないため理想的な材料となる。 The low thermal expansion alloy material is applied for the purpose of suppressing thermal deformation due to temperature changes of precision equipment in various advanced fields. If the coefficient of thermal expansion is zero, thermal deformation does not occur due to temperature changes, making it an ideal material.
　航空・宇宙機器や計測機器等の部材には低温域で稼働するものがあり、－１００℃以下で使用される場合がある。このような低温域においても組織変化に伴う熱膨張係数の急激な変化がなく、１００℃から－７０℃の間の熱膨張係数が事実上ゼロ膨張とみなすことのできる０±０．２ｐｐｍ/℃の範囲である合金材料が望まれている。 Some parts such as aerospace equipment and measuring equipment operate in the low temperature range, and may be used at -100 ° C or lower. Even in such a low temperature range, there is no sudden change in the coefficient of thermal expansion due to structural changes, and the coefficient of thermal expansion between 100 ° C and -70 ° C can be regarded as virtually zero expansion at 0 ± 0.2 ppm / ° C. An alloy material within the range of is desired.
　現在、低熱膨張材料として、スーパーインバー（ＳＩ）に代表されるＦｅ-Ｎｉ-Ｃｏ系低熱膨張合金が工業的に利用されている。ＳＩは、室温付近の熱膨張係数は１～２ｐｐｍ／℃であるＦｅ－３６％Ｎｉ合金（インバー）のＮｉの一部をＣｏに置き換えることで低膨張化させたもので、Ｆｅ－３２％Ｎｉ－５％Ｃｏ合金であり、室温付近の熱膨張係数は１ｐｐｍ/℃以下になる。 Currently, Fe-Ni-Co-based low thermal expansion alloys typified by Super Invar (SI) are industrially used as low thermal expansion materials. SI is a low expansion of Fe-36% Ni alloy (Invar) having a coefficient of thermal expansion near room temperature of 1 to 2 ppm / ° C by replacing a part of Ni with Co. Fe-32% Ni It is a -5% Co alloy and has a coefficient of thermal expansion near room temperature of 1 ppm / ° C or less.
　このため、ＳＩは熱変形による精度低下を抑える目的で精密装置部材に適用される。しかし、ＮｉをＣｏで置換することによりＮｉ量が低下してオーステナイトが不安定化し、マルテンサイト生成開始温度（以下、Ｍｓ点と記す）が高温側に移動する。ＳＩのＭｓ点は不純物量によって多少変化するが、概ね‐４０℃前後まで上昇する。したがって、この温度以下ではマルテンサイト組織を生成して熱膨張係数が急激に増加し、低熱膨張性を失うため、低温域で稼働する航空・宇宙機器や計測機器等の部材への適用が制限される（特許文献１の段落０００３、００３４）。当然のことながら、１００℃から－７０℃の温度範囲でのゼロ膨張を実現することはできない。 For this reason, SI is applied to precision equipment members for the purpose of suppressing a decrease in accuracy due to thermal deformation. However, by substituting Ni with Co, the amount of Ni decreases, austenite becomes unstable, and the martensite formation start temperature (hereinafter referred to as Ms point) moves to the higher temperature side. The Ms point of SI changes slightly depending on the amount of impurities, but rises to about -40 ° C. Therefore, below this temperature, a martensite structure is generated, the coefficient of thermal expansion increases sharply, and low thermal expansion is lost, so application to members such as aerospace equipment and measuring equipment operating in the low temperature range is restricted. (Paragraphs 0003 and 0034 of Patent Document 1). As a matter of course, zero expansion in the temperature range of 100 ° C to −70 ° C cannot be achieved.
　一方、インバーは、Ｍｓ点が－１９６℃以下であり、－１９６℃以下でも組織が変化せず低熱膨張性を保持するため、暴露温度が－１００℃より低温となる航空・宇宙機器や計測機器等にも適用可能である。しかし、熱膨張係数が１～２ｐｐｍ／℃でＳＩより大きく、ゼロ膨張とは大きく隔たりがあるため熱変形抑制効果が不十分であり、高度な要求に対応できないという問題があり、超精密装置部材への適用が制限される（特許文献１の段落００２４）。 On the other hand, Invar has an Ms point of -196 ° C or lower, and the structure does not change even at -196 ° C or lower and maintains low thermal expansion. Therefore, the exposure temperature of Invar is lower than -100 ° C for aerospace equipment and measuring equipment. It can also be applied to. However, the coefficient of thermal expansion is 1 to 2 ppm / ° C., which is larger than SI, and there is a large gap from zero expansion. Therefore, the effect of suppressing thermal deformation is insufficient, and there is a problem that it cannot meet high demands. (Paragraph 0024 of Patent Document 1).
　また、特許文献２では、特定組成の合金粉末にレーザーまたは電子ビームを照射して溶融・急速凝固および積層造形することによりデンドライト２次アーム間隔を５μｍ以下とすることにより、０．５ｐｐｍ／℃以下の熱膨張係数およびＳＩでは得られなかった低温安定性の両立を図ることが提案されている。 Further, in Patent Document 2, the dendrite secondary arm spacing is set to 5 μm or less by irradiating an alloy powder having a specific composition with a laser or an electron beam to melt, rapidly solidify, and laminate, to 0.5 ppm / ° C or less. It has been proposed to achieve both the coefficient of thermal expansion of the above and the low temperature stability that could not be obtained by SI.
　しかし、特許文献２の実施例によると、Ｎｏ．７を除いて熱膨張係数は０．４ｐｐｍ／℃前後であり、安定してゼロ膨張を示す材料は得られていない。また、低温域で稼働する機器は、低温安定性が得られる温度が低ければ低いほどよく、インバー合金と同等の安定性が望まれるが、特許文献２の合金では、インバー合金と同等のＭｓ点－１９６℃以下を安定して得ることはできていない。 However, according to the example of Patent Document 2, No. Except for 7, the coefficient of thermal expansion is around 0.4 ppm / ° C, and no material showing stable zero expansion has been obtained. Further, in a device operating in a low temperature range, the lower the temperature at which low temperature stability can be obtained, the better, and the same stability as the Invar alloy is desired. However, in the alloy of Patent Document 2, the Ms point equivalent to that of the Invar alloy is obtained. It has not been possible to stably obtain a temperature of -196 ° C or lower.
特開２０１１－１７４８５４号公報Japanese Unexamined Patent Publication No. 2011-174854 国際公開第２０１９／０４４０９３号International Publication No. 2019/044093
　以上のように、ＳＩは－１００℃のような低温においてはマルテンサイト組織を生成して熱膨張係数が急激に増加し、インバーは熱膨張係数が１～２ｐｐｍ／℃で、熱変形抑制効果が不十分である。さらに、特許文献２の低熱膨張合金は、安定してゼロ膨張を示すとはいえず、かつインバー合金と同程度の低温安定性は得られない。したがって、１００℃から－７０℃の間でゼロ膨張を実現でき、かつインバー合金と同程度の低温安定性が得られる材料は未だ得られていない。 As described above, SI forms a martensite structure at a low temperature such as -100 ° C, and the coefficient of thermal expansion increases sharply. Invar has a coefficient of thermal expansion of 1 to 2 ppm / ° C and has an effect of suppressing thermal deformation. Insufficient. Further, the low thermal expansion alloy of Patent Document 2 cannot be said to stably exhibit zero expansion, and cannot obtain the same low temperature stability as the Invar alloy. Therefore, a material that can realize zero expansion between 100 ° C. and −70 ° C. and can obtain low temperature stability comparable to that of Invar alloy has not yet been obtained.
　本発明は、１００℃から－７０℃の間の平均熱膨張係数がゼロ膨張とみなすことができる０±０．２ｐｐｍ／℃であり、インバー合金と同程度の低温安定性が得られる低熱膨張合金およびその製造方法を提供することを目的とする。 In the present invention, the average coefficient of thermal expansion between 100 ° C. and −70 ° C. is 0 ± 0.2 ppm / ° C., which can be regarded as zero expansion, and a low thermal expansion alloy having the same low temperature stability as an Invar alloy can be obtained. And its manufacturing method.
　本発明によれば、以下の（１）～（４）が提供される。 According to the present invention, the following (1) to (4) are provided.
　（１）質量％で、
　Ｃ：０．０１５％以下、
　Ｓｉ：０．１０％以下、
　Ｍｎ：０．１５％以下、
　Ｎｉ：３５．０～３７．０％、
　Ｃｏ：２．０％未満を含有し、
　かつＮｉ＋０．８Ｃｏ：３５．０～３７．０％であり、
　残部がＦｅおよび不可避不純物からなり、デンドライト２次アーム間隔が５μｍ以下である凝固組織を有し、１００～－７０℃の平均熱膨張係数が０±０．２ｐｐｍ／℃の範囲で、かつＭｓ点が－１９６℃以下であることを特徴とする低熱膨張合金。 (1) By mass%
C: 0.015% or less,
Si: 0.10% or less,
Mn: 0.15% or less,
Ni: 35.0-37.0%,
Co: Containing less than 2.0%,
And Ni + 0.8Co: 35.0 to 37.0%,
The balance is composed of Fe and unavoidable impurities, has a solidified structure with a dendrite secondary arm spacing of 5 μm or less, an average coefficient of thermal expansion of 100 to −70 ° C. in the range of 0 ± 0.2 ppm / ° C., and Ms point. A low thermal expansion alloy characterized by a temperature of -196 ° C or lower.
　（２）Ｃ、Ｓｉ、Ｍｎの含有量が、Ｃ×７＋Ｓｉ×１．５＋Ｍｎ≦０．４０を満足することを特徴とする上記（１）に記載の低熱膨張合金。 (2) The low thermal expansion alloy according to (1) above, wherein the contents of C, Si, and Mn satisfy C × 7 + Si × 1.5 + Mn ≦ 0.40.
　（３）上記（１）または（２）に記載の組成を有する低熱膨張合金素材を、レーザーまたは電子ビームによって、溶融・凝固させて積層造形させ、１００～－７０℃の平均熱膨張係数が０±０．２ｐｐｍ／℃の範囲で、かつＭｓ点が－１９６℃以下の低熱膨張合金を製造することを特徴とする低熱膨張合金の製造方法。 (3) The low thermal expansion alloy material having the composition according to (1) or (2) above is melted and solidified by a laser or an electron beam to form a laminate, and the average coefficient of thermal expansion at 100 to −70 ° C. is 0. A method for producing a low thermal expansion alloy, which comprises producing a low thermal expansion alloy in the range of ± 0.2 ppm / ° C. and having an Ms point of -196 ° C. or lower.
　（４）前記低熱膨張合金素材は、粉末であることを特徴とする上記（３）に記載の低熱膨張合金の製造方法。 (4) The method for producing a low thermal expansion alloy according to (3) above, wherein the low thermal expansion alloy material is a powder.
　本発明によれば、１００℃から－７０℃の間の平均熱膨張係数がゼロ膨張とみなすことができる０±０．２ｐｐｍ／℃であり、インバー合金と同程度の低温安定性が得られる低熱膨張合金およびその製造方法が提供される。 According to the present invention, the average coefficient of thermal expansion between 100 ° C. and −70 ° C. is 0 ± 0.2 ppm / ° C., which can be regarded as zero expansion, and low heat stability comparable to that of Invar alloy can be obtained. Expansion alloys and methods for producing them are provided.
本発明の実施例に用いたアトマイズ装置を示す概念図である。It is a conceptual diagram which shows the atomizing apparatus used in the Example of this invention. 図１のアトマイズ装置により得られた球状粉末を示す光学顕微鏡写真である。It is an optical micrograph which shows the spherical powder obtained by the atomizing apparatus of FIG. ＤＡＳと冷却速度との関係を示す図である。It is a figure which shows the relationship between DAS and a cooling rate. 本発明組成合金のレーザー積層造形物のＤＡＳを示す写真である。It is a photograph which shows the DAS of the laser laminated model of the composition alloy of this invention. 純銅型鋳造物のＤＡＳを示す写真である。It is a photograph which shows DAS of a pure copper type casting. 純銅型を示す図である。It is a figure which shows the pure copper mold.
　上述のように、Ｆｅ-Ｎｉ-Ｃｏ系低熱膨張合金の熱膨張係数を決定する最大の要因はＣｏの含有量であるが、Ｃｏ添加により相対的にＮｉ量が低下してオーステナイトが不安定化し、Ｍｓが上昇する。最も低熱膨張となる３２％Ｎｉ-５％ＣｏのＳＩではＭｓ点が‐４０℃前後となるため、これより低温での適用ができない。したがって、Ｃｏで低熱膨張化を図る限り室温付近から-７０℃の温度範囲で安定して熱膨張係数を０±０．２ｐｐｍ/℃にすることは困難である。 As described above, the largest factor that determines the coefficient of thermal expansion of Fe-Ni-Co-based low thermal expansion alloys is the Co content, but the addition of Co relatively reduces the Ni content and destabilizes austenite. , Ms rises. At SI of 32% Ni-5% Co, which has the lowest thermal expansion, the Ms point is around -40 ° C, so it cannot be applied at lower temperatures. Therefore, it is difficult to stably set the coefficient of thermal expansion to 0 ± 0.2 ppm / ° C. in the temperature range from around room temperature to −70 ° C. as long as Co is used for low thermal expansion.
　本発明者らは、従来のＦｅ-Ｎｉ-Ｃｏ系低熱膨張合金に見られるＣｏによるＭｓ点上昇を伴わない低熱膨張化技術について検討した。その結果、Ｆｅ－３６％Ｎｉ組成を基本として、Ｃ、Ｓｉ、Ｍｎを低減するとともに、ミクロ組織を小さくしてデンドライト２次アーム間隔を５μｍ以下とすることにより、１００℃から－７０℃の間の熱膨張係数がゼロ膨張とみなすことができる０±０．２ｐｐｍ／℃で、かつインバー合金と同程度の低温安定性が得られることを見出した。 The present inventors have investigated a low thermal expansion technique that does not involve an increase in the Ms point due to Co, which is found in conventional Fe-Ni-Co low thermal expansion alloys. As a result, based on the Fe-36% Ni composition, C, Si, and Mn are reduced, the microstructure is reduced, and the dendrite secondary arm spacing is set to 5 μm or less, so that the temperature is between 100 ° C. and −70 ° C. It was found that the coefficient of thermal expansion of the above is 0 ± 0.2 ppm / ° C., which can be regarded as zero expansion, and low temperature stability comparable to that of Invar alloy can be obtained.
　本発明はこれらの知見に基づいて完成されたものである。 The present invention has been completed based on these findings.
　以下、本発明の限定理由について、化学成分および製造条件に分けて説明する。
　なお、以下の説明において、特に断わらない限り成分における％表示は質量％であり、αは１００～-７０℃の平均熱膨張係数である。 Hereinafter, the reasons for limiting the present invention will be described separately for chemical components and production conditions.
In the following description, unless otherwise specified, the% representation of the components is mass%, and α is the average coefficient of thermal expansion of 100 to −70 ° C.
　［化学成分］
　Ｃ：０．０１５％以下
　Ｃは本発明に係る低熱膨張合金のαを著しく増加させる元素であり、低いことが望ましい。Ｃは０．０１５％を超えて含有すると、後述する他の元素の含有量によってもαが０±０．２ｐｐｍ／℃の範囲を超えるため、Ｃ含有量を０．０１５％以下とする。 [Chemical composition]
C: 0.015% or less C is an element that significantly increases α of the low thermal expansion alloy according to the present invention, and is preferably low. If C is contained in excess of 0.015%, α exceeds the range of 0 ± 0.2 ppm / ° C depending on the content of other elements described later, so the C content is set to 0.015% or less.
　Ｓｉ：０．１０％以下
　Ｓｉは合金中の酸素を低減する目的で添加する元素である。しかし、Ｓｉは本発明に係る低熱膨張合金のαを著しく増加させる元素であり、低いことが望ましい。その含有量が０．１０％超ではＣと同様にαの増加が無視できなくなる。したがって、Ｓｉ含有量を０．１０％以下とする。 Si: 0.10% or less Si is an element added for the purpose of reducing oxygen in the alloy. However, Si is an element that remarkably increases α of the low thermal expansion alloy according to the present invention, and it is desirable that it is low. If the content exceeds 0.10%, the increase in α cannot be ignored as in C. Therefore, the Si content is set to 0.10% or less.
　Ｍｎ：０．１５％以下
　ＭｎはＳｉと同様に脱酸に有効な元素である。しかし、Ｍｎは本発明に係る低熱膨張合金において、αを著しく増加させる元素であり、低いことが望ましい。その含有量が０．１５％を超えるとＣと同様にαの増加が無視できなくなる。したがって、Ｍｎ含有量を０．１５％以下とする。 Mn: 0.15% or less Mn is an element effective for deoxidation like Si. However, Mn is an element that significantly increases α in the low thermal expansion alloy according to the present invention, and is preferably low. If the content exceeds 0.15%, the increase in α cannot be ignored as in C. Therefore, the Mn content is set to 0.15% or less.
　Ｎｉ：３５．０～３７．０％
　Ｎｉは合金の基本的なαを決定する元素である。αを０±０．２ｐｐｍ／℃の範囲にするためには、Ｃｏ量に応じて後述の範囲に調整する必要がある。Ｎｉが３５．０％未満、または３７．０％超では、Ｃｏ量に応じた調整および後述する製造条件によってもαを０±０．２ｐｐｍ／℃の範囲にすることは困難である。したがって、Ｎｉの含有量を３５．０～３７．０％の範囲とする。 Ni: 35.0 to 37.0%
Ni is an element that determines the basic α of an alloy. In order to set α in the range of 0 ± 0.2 ppm / ° C, it is necessary to adjust it to the range described later according to the amount of Co. When Ni is less than 35.0% or more than 37.0%, it is difficult to set α in the range of 0 ± 0.2 ppm / ° C. even by adjusting according to the amount of Co and the production conditions described later. Therefore, the Ni content is set in the range of 35.0 to 37.0%.
　Ｃｏ：２．０％未満
　ＣｏはＮｉとともにαを決定する重要な元素であり、Ｎｉ単独添加の場合より小さなαを得るために添加する元素である。しかし、Ｃｏが２．０％以上では後述のＮｉ量とＣｏ量の関係式に基づいて得られるＮｉ量が減少し、オーステナイトが不安定化するため、Ｍｓ点が－１９６℃より高温になる。したがって、Ｃｏの含有量を２．０％未満とする。安衛法特化則の所定の管理・対策を不要にする観点からは１．０％以下が好ましい。 Co: Less than 2.0% Co is an important element that determines α together with Ni, and is an element added to obtain a smaller α than when Ni alone is added. However, when Co is 2.0% or more, the amount of Ni obtained based on the relational expression between the amount of Ni and the amount of Co described later decreases, and austenite becomes unstable, so that the Ms point becomes higher than -196 ° C. Therefore, the Co content is set to less than 2.0%. 1.0% or less is preferable from the viewpoint of eliminating the need for the prescribed management and measures of the Safety and Health Law Specialization Regulations.
　Ｎｉ＋０．８Ｃｏ：３５．０～３７．０％
　Ｆｅ－Ｎｉ－Ｃｏ合金は、前記のＮｉ量、Ｃｏ量の範囲でかつ、Ｎｉ＋０．８×Ｃｏで表されるＮｉ当量（Ｎｉｅｑ．）が一定範囲において顕著な低熱膨張性が得られる。Ｎｉ当量は、３５．０％未満でも、３７．０％超でも、αが０±０．２ｐｐｍ／℃の範囲に入らなくなる。したがって、Ｎｉ当量であるＮｉ＋０．８Ｃｏを３５．０～３７．０％の範囲とする。 Ni + 0.8Co: 35.0-37.0%
The Fe—Ni—Co alloy can obtain remarkable low thermal expansion property in the above-mentioned Ni amount and Co amount range and in a certain range of Ni equivalent (Nieq.) Expressed by Ni + 0.8 × Co. Even if the Ni equivalent is less than 35.0% or more than 37.0%, α does not fall within the range of 0 ± 0.2 ppm / ° C. Therefore, the Ni equivalent of Ni + 0.8Co is set in the range of 35.0 to 37.0%.
　Ｃ×７＋Ｓｉ×１．５＋Ｍｎ≦０．４０
　本発明のＦｅ－Ｎｉ－Ｃｏ合金において、Ｃ量、Ｓｉ量およびＭｎ量を上記範囲に規定した上で、Ｃ×７＋Ｓｉ×１．５＋Ｍｎで表される式の値を０．４０以下とすることにより、顕著な低熱膨張性が得られる。したがって、Ｃ×７＋Ｓｉ×１．５＋Ｍｎ≦０．４０とすることが好ましい。 C × 7 + Si × 1.5 + Mn ≦ 0.40
In the Fe—Ni—Co alloy of the present invention, the amount of C, the amount of Si, and the amount of Mn are defined in the above ranges, and the value of the formula represented by C × 7 + Si × 1.5 + Mn is 0.40 or less. Therefore, a remarkable low thermal expansion property is obtained. Therefore, it is preferable to set C × 7 + Si × 1.5 + Mn ≦ 0.40.
　本発明において、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｃｏ以外の残部は、Ｆｅおよび不可避的不純物である。 In the present invention, the balance other than C, Si, Mn, Ni and Co is Fe and unavoidable impurities.
　［凝固組織］
　凝固組織を微細化することによりαを小さくすることができる。その理由は、前述のように、組織の微細化によってＮｉのミクロ偏析が軽減するためであると考えられる。本発明に係る低熱膨張合金は、デンドライト２次アーム（ＤＡＳ）間隔が５μｍ以下となるように凝固組織を微細化する。上記組成の合金においてＤＡＳ間隔を５μｍ以下とすることにより、αを０±０．２ｐｐｍ／℃の範囲とすることができる。 [Coagulation tissue]
Α can be reduced by making the solidified structure finer. The reason is considered to be that the microsegregation of Ni is reduced by the miniaturization of the structure as described above. In the low thermal expansion alloy according to the present invention, the solidified structure is refined so that the dendrite secondary arm (DAS) spacing is 5 μm or less. By setting the DAS interval to 5 μm or less in the alloy having the above composition, α can be set in the range of 0 ± 0.2 ppm / ° C.
　［Ｍｓ点］
　本発明に係る低熱膨張合金は、Ｃｏ含有量が少なくＮｉ含有量が３５％以上で、かつ上述のような微細な凝固組織を有することから、Ｍｓ点がインバー合金と同程度の－１９６℃以下であり、インバー合金と同程度の優れた低温安定性が得られる。 [Ms point]
The low thermal expansion alloy according to the present invention has a low Co content, a Ni content of 35% or more, and has a fine solidification structure as described above. Therefore, the Ms point is -196 ° C. or lower, which is about the same as that of the Invar alloy. Therefore, excellent low temperature stability comparable to that of Invar alloy can be obtained.
　［製造条件］
　上記組成を有する低熱膨張合金素材を、レーザーまたは電子ビームによって、溶融・凝固させて積層造形させる。これにより低熱膨張合金素材が溶融された後、急冷され、ＤＡＳ間隔を５μｍ以下の微細な組織とすることができる。これによりＮｉのミクロ偏析が軽減し、αを０±０．２ｐｐｍ／℃の範囲とすることができる。ただし、ＤＡＳが５μｍ以下の微細な凝固組織が得られる溶融・凝固条件を実現できれば、いずれの方法も適用可能である。 [Manufacturing conditions]
The low thermal expansion alloy material having the above composition is melted and solidified by a laser or an electron beam to form a laminated structure. As a result, the low thermal expansion alloy material is melted and then rapidly cooled, so that the DAS interval can be made into a fine structure of 5 μm or less. As a result, the microsegregation of Ni is reduced, and α can be set in the range of 0 ± 0.2 ppm / ° C. However, any method can be applied as long as the melting / solidifying conditions for obtaining a fine solidified structure having a DAS of 5 μm or less can be realized.
　具体的には、上記範囲内の組成を有する合金素材として合金粉末を準備し、レーザーまたは電子ビームによって、溶融・凝固させて積層造形させることによりＤＡＳ間隔を５μｍ以下の微細凝固組織の合金とすることができる。 Specifically, an alloy powder is prepared as an alloy material having a composition within the above range, melted and solidified by a laser or an electron beam, and laminated to form an alloy having a DAS interval of 5 μm or less. be able to.
　積層造形においては、合金の凝固時の冷却速度を３０００℃／ｓｅｃ．以上とすることにより、ＤＡＳ間隔が５μｍ以下の微細凝固組織を得ることができる。レーザーまたは電子ビームであれば、この冷却速度を満たす。 In laminated molding, the cooling rate at the time of solidification of the alloy is 3000 ° C./sec. With the above, a fine solidified structure having a DAS interval of 5 μm or less can be obtained. A laser or electron beam will satisfy this cooling rate.
　一方、後掲の図３に示すように、従来の鋳造プロセスの中では、最も冷却速度が大きいダイカストによってもＤＡＳを５μｍ以下とするには冷却速度が不十分であり、まして本発明の合金のような高融点の鉄系合金の鋳造が可能である銅合金型の場合には、後掲の図５に示すように、ＤＡＳを５μｍ以下にすることは到底できず、所期の特性を得ることは不可能である。 On the other hand, as shown in FIG. 3 below, in the conventional casting process, the cooling rate is insufficient to reduce the DAS to 5 μm or less even by the die casting having the highest cooling rate, much less the alloy of the present invention. In the case of a copper alloy type capable of casting such a high melting point iron-based alloy, as shown in FIG. 5 below, it is impossible to reduce the DAS to 5 μm or less, and the desired characteristics are obtained. That is impossible.
　本発明によれば、１００℃から－７０℃の間の平均熱膨張係数がゼロ膨張とみなすことができる０±０．２ｐｐｍ／℃であり、インバー合金と同程度の低温安定性が得られる低熱膨張合金が得られる。 According to the present invention, the average coefficient of thermal expansion between 100 ° C. and −70 ° C. is 0 ± 0.2 ppm / ° C., which can be regarded as zero expansion, and low heat stability comparable to that of Invar alloy can be obtained. An expansion alloy is obtained.
　本発明に係る低熱膨張合金は、従来の低膨張合金では適用が制限されていた、航空・宇宙分野を始めとする低温域で稼働する各種精密装置部材への適用が可能となり、当該分野における高精度化に大きく貢献する。 The low thermal expansion alloy according to the present invention can be applied to various precision equipment members operating in a low temperature region including the aerospace field, which has been restricted in application with the conventional low expansion alloy, and is highly applicable in the field. Greatly contributes to accuracy.
　また、Ｆｅ-Ｎｉ-Ｃｏ系低熱膨張合金であるＳＩでは、Ｃｏを５％程度含有しているため、材料費が高くなるとともに、安衛法特化則の１％超Ｃｏ含有物質に該当し、所定の管理・対策が必要となる。これに対して、本発明に係る低熱膨張合金は、Ｃｏが２％未満と少なく、材料費の高騰を抑制できるとともに、Ｃｏが１ｍａｓｓ％以下の場合は、その適用に際してＣｏ含有の表示のみを行えばよく、安衛法特化則の所定の管理・対策が不要となる。 In addition, SI, which is a Fe-Ni-Co-based low thermal expansion alloy, contains about 5% of Co, so that the material cost is high and it corresponds to a substance containing more than 1% Co in the Safety Law Specialization Regulations. Prescribed management and measures are required. On the other hand, the low thermal expansion alloy according to the present invention has a low Co content of less than 2%, which can suppress an increase in material cost, and when the Co content is 1 mass% or less, only the Co content is indicated at the time of application. All that is required is that the prescribed management and measures of the Safety and Health Law Specialization Regulations are not required.
　以下、本発明の実施例について説明する。
　表１に示す化学成分および組成の合金の積層造形、ならびに純銅型への鋳造によって試料を作製した。 Hereinafter, examples of the present invention will be described.
Samples were prepared by laminating the alloys of the chemical components and compositions shown in Table 1 and casting them into a pure copper mold.
　積層造形の試料は、表１に示す化学組成の合金を高周波誘導炉で溶解し、図１に示すアトマイズ装置を用いて、溶融した金属を滴下し、ノズルから不活性ガス（本例では窒素ガス）を噴霧することで液滴に分断するとともに急速凝固させて球状粉末を得た。その後、ふるい分けして図２に示す粒径１０～４５μｍの造形用粉末を得た。レーザー式積層造形装置を用いて、出力３００Ｗ、レーザー移動速度１０００ｍｍ/秒、レーザー走査ピッチ０．１ｍｍ、粉末積層厚さ０．０４ｍｍの条件で造形用粉末を積層造形し、φ１０×Ｌ１００の試料を作製した。 For the laminated molding sample, the alloy having the chemical composition shown in Table 1 is melted in a high-frequency induction furnace, the molten metal is dropped using the atomizing apparatus shown in FIG. 1, and an inert gas (nitrogen gas in this example) is dropped from the nozzle. ) Was sprayed to divide into droplets and rapidly solidify to obtain a spherical powder. Then, it was sifted to obtain a modeling powder having a particle size of 10 to 45 μm shown in FIG. Using a laser additive manufacturing device, the modeling powder is laminated and modeled under the conditions of output 300 W, laser moving speed 1000 mm / sec, laser scanning pitch 0.1 mm, and powder layered thickness 0.04 mm, and a sample of φ10 × L100 is prepared. Made.
　鋳造の試料は、高周波誘導炉で溶解した合金溶湯約１００ｇを、鋳込み温度１５５０℃で図６に示す純銅型に鋳造し、鋳型底の先端部から採取した。 As a casting sample, about 100 g of molten alloy melted in a high-frequency induction furnace was cast into a pure copper mold shown in FIG. 6 at a casting temperature of 1550 ° C., and the sample was collected from the tip of the mold bottom.
　図３は、本発明試料の光学顕微鏡組織観察によって実測したＤＡＳと、以下の文献１に記載のＤＡＳと冷却速度の関係の外挿線から、試料の冷却速度を推定するもので、以下の文献２～４の情報から得られた各種鋳型の冷却速度も併記した。
　　　　Ｒ＝（ＤＡＳ／７０９）1/-0.386　・・・（１）
Ｒ：冷却速度（℃／ｍｉｎ．）、ＤＡＳ：デンドライト２次アーム間隔（μｍ）
　文献１：「鋳鋼の生産技術」P378、素形材センタ―
　文献２：「鋳物」、第63巻(1991)第11号、P915
　文献３：「鋳造工学」、第68巻(1996)第12号、P1076
　文献４：「素形材」、Vol.54（2013）No.1、P13 FIG. 3 shows the cooling rate of the sample estimated from the DAS measured by observing the microstructure of the sample of the present invention and the extrapolation line of the relationship between the DAS and the cooling rate described in Document 1 below. The cooling rates of various molds obtained from the information of 2 to 4 are also shown.
R = (DAS / 709) 1 / -0.386 ... (1)
R: Cooling rate (° C / min.), DAS: Dendrite secondary arm spacing (μm)
Reference 1: "Cast Steel Production Technology" P378, Raw Material Center
Reference 2: "Casting", Vol. 63 (1991) No. 11, P915
Reference 3: "Casting Engineering", Vol. 68 (1996) No. 12, P1076
Reference 4: "Shaping Material", Vol.54 (2013) No.1, P13
　　試料は造形用ベースプレートから放電ワイヤーカットで切り離した後、φ６×５０ｍｍの熱膨張試験片に機械加工し、レーザー干渉式熱膨張計を用いて２℃／ｍｉｎ．で昇温しながら熱膨張を測定し、得られた熱膨張曲線からαを求めた。 The sample was separated from the modeling base plate by a discharge wire cut, then machined into a thermal expansion test piece of φ6 x 50 mm, and used at 2 ° C / min with a laser interference type thermal expansion meter. The thermal expansion was measured while raising the temperature with, and α was obtained from the obtained thermal expansion curve.
　また、Ｍｓ点は前記熱膨張試験片を前記熱膨張計にセットし、液体窒素により３℃／ｍｉｎ．で冷却しながら熱膨張を測定し、熱膨張曲線が急激に変化した温度から求めた。 At the Ms point, the thermal expansion test piece was set in the thermal expansion meter, and liquid nitrogen was used at 3 ° C./min. The thermal expansion was measured while cooling with, and it was obtained from the temperature at which the thermal expansion curve changed abruptly.
　前記の測定で熱膨張曲線の急激な変化が認められなかった試料については、液体窒素に１５分間浸漬した後、ミクロ組織を観察し、マルテンサイト組織の有無を確認した。 For the sample in which no rapid change in the thermal expansion curve was observed in the above measurement, the sample was immersed in liquid nitrogen for 15 minutes, and then the microstructure was observed to confirm the presence or absence of the martensite structure.
　表１の本発明例Ｎｏ．１～８は、化学成分および組成が本発明の範囲内であり、かつ粉末積層造形により製造されたものであり、いずれも、１００～-７０℃間の平均熱膨張係数であるαが０±０．２ｐｐｍ／℃の範囲およびＭｓ点が－１９６℃以下であった。Ｎｏ．４およびＮｏ．８は、類似組成であるが、Ｎｏ．４は７Ｃ＋１．５Ｓｉ＋Ｍｎが０．４以下であり、Ｎｏ．８が０．４を超えている。これらを比較すると、αがいずれも０±０．２ｐｐｍ／℃の範囲内であったが、７Ｃ＋１．５Ｓｉ＋Ｍｎが０．４以下を満たすＮｏ．４のほうがＮｏ．８よりもαの値が小さくなった。 Example No. of the present invention in Table 1. 1 to 8 are those whose chemical composition and composition are within the range of the present invention and are manufactured by powder additive manufacturing, and all of them have an α of 0 ± which is an average coefficient of thermal expansion between 100 and −70 ° C. The range of 0.2 ppm / ° C. and the Ms point were -196 ° C. or lower. No. 4 and No. No. 8 has a similar composition, but No. No. 4 has 7C + 1.5Si + Mn of 0.4 or less, and No. 8 is over 0.4. Comparing these, α was in the range of 0 ± 0.2 ppm / ° C., but No. 7C + 1.5Si + Mn satisfied 0.4 or less. No. 4 is No. The value of α became smaller than 8.
　図４は本発明例Ｎｏ．７の光学顕微鏡写真であるが、この光学顕微鏡写真からＮｏ．７のＤＡＳを実測した結果、１．４μｍと５μｍ以下であった。また、このＤＡＳの値から、冷却速度は１．５×１０５℃／ｓｅｃ．と推定した。 FIG. 4 shows Example No. of the present invention. It is the optical micrograph of No. 7. From this optical micrograph, No. As a result of actually measuring the DAS of 7, it was 1.4 μm and 5 μm or less. Further, the value of the DAS, the cooling rate is 1.5 × 10 5 ℃ / sec. Estimated.
　以上の結果から、本発明合金は航空・宇宙分野の厳しい要求にも応えられる特性を持っていることが確認された。 From the above results, it was confirmed that the alloy of the present invention has characteristics that can meet the strict requirements in the aerospace field.
　一方、比較例ＡのＮｏ．１１～１７は、それぞれ発明例のＮｏ．１～７と化学成分および組成は同じであるが、純銅型に鋳造したものであり、ＤＡＳが５μｍを超えた本発明範囲外のものである。図５は比較例ＡのＮｏ．１７の光学顕微鏡写真であるが、この写真からＮｏ．１７の純銅型に鋳造した場合のＤＡＳを実測した結果１６μｍであった。このため、Ｎｏ．１１～１７のいずれもαが０±０．２ｐｐｍ／℃の範囲を外れた。 On the other hand, No. of Comparative Example A. Nos. 11 to 17 are No. 1 of the invention examples, respectively. It has the same chemical composition and composition as 1 to 7, but it is cast in a pure copper mold and has a DAS of more than 5 μm, which is outside the scope of the present invention. FIG. 5 shows No. 5 of Comparative Example A. It is an optical microscope photograph of 17, and from this photograph, No. The actual measurement result of DAS when cast into 17 pure copper molds was 16 μm. Therefore, No. In all of 11 to 17, α was out of the range of 0 ± 0.2 ppm / ° C.
　また比較例ＢのＮｏ．１８～２４は化学成分および組成が本発明範囲外のもので、積層造形、ならびに純銅型に鋳造して試料を作製したものである。Ｎｏ．１８はＣが、Ｎｏ．１９はＳｉが、Ｎｏ．２０はＭｎが、Ｎｏ．２２はＮｉおよびＮｉ当量が上限超であったため、製造方法によらず、いずれもαが０±０．２ｐｐｍ／℃の範囲を外れた値となった。Ｎｏ．２３はＣｏが下限超であったため、製造方法によらず、いずれもαが０±０．２ｐｐｍ／℃の範囲を外れた値となった。Ｎｏ．２１はＮｉが下限未満であったため、製造方法によらず、αが０±０．２ｐｐｍ／℃の範囲を外れた値となり、また、Ｍｓ点が－１９６℃より高温であった。比較例ＢのＮｏ．２４は従来合金のＳＩで、製造方法によらず、Ｍｓ点が－１９６℃より高温であった。 Also, No. of Comparative Example B. Nos. 18 to 24 have chemical components and compositions outside the scope of the present invention, and are obtained by laminating molding and casting into a pure copper mold to prepare a sample. No. In 18, C is No. In No. 19, Si is No. In No. 20, Mn is No. Since the Ni and Ni equivalents of No. 22 exceeded the upper limit, α was a value outside the range of 0 ± 0.2 ppm / ° C. regardless of the production method. No. Since Co was above the lower limit in No. 23, α was a value outside the range of 0 ± 0.2 ppm / ° C. regardless of the production method. No. Since Ni was less than the lower limit of No. 21, α was a value outside the range of 0 ± 0.2 ppm / ° C., and the Ms point was higher than -196 ° C. regardless of the production method. Comparative Example B No. Reference numeral 24 denotes SI of the conventional alloy, and the Ms point was higher than -196 ° C. regardless of the production method.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Claims (4)

  1. 　質量％で、
    　Ｃ：０．０１５％以下、
    　Ｓｉ：０．１０％以下、
    　Ｍｎ：０．１５％以下、
    　Ｎｉ：３５．０～３７．０％、
    　Ｃｏ：２．０％未満を含有し、
    　かつＮｉ＋０．８Ｃｏ：３５．０～３７．０％であり、
    　残部がＦｅおよび不可避不純物からなり、デンドライト２次アーム間隔が５μｍ以下である凝固組織を有し、１００～－７０℃の平均熱膨張係数が０±０．２ｐｐｍ／℃の範囲で、かつＭｓ点が－１９６℃以下であることを特徴とする低熱膨張合金。     By mass%
    C: 0.015% or less,
    Si: 0.10% or less,
    Mn: 0.15% or less,
    Ni: 35.0-37.0%,
    Co: Containing less than 2.0%,
    And Ni + 0.8Co: 35.0 to 37.0%,
    The balance is composed of Fe and unavoidable impurities, has a solidified structure with a dendrite secondary arm spacing of 5 μm or less, an average coefficient of thermal expansion of 100 to −70 ° C. in the range of 0 ± 0.2 ppm / ° C., and Ms point. A low thermal expansion alloy characterized by a temperature of -196 ° C or lower.
  2. 　Ｃ、Ｓｉ、Ｍｎの含有量が、Ｃ×７＋Ｓｉ×１．５＋Ｍｎ≦０．４０を満足することを特徴とする請求項１に記載の低熱膨張合金。 The low thermal expansion alloy according to claim 1, wherein the contents of C, Si, and Mn satisfy C × 7 + Si × 1.5 + Mn ≦ 0.40.
  3. 　請求項１または請求項２に記載の組成を有する低熱膨張合金素材を、レーザーまたは電子ビームによって、溶融・凝固させて積層造形させ、１００～－７０℃の平均熱膨張係数が０±０．２ｐｐｍ／℃の範囲で、かつＭｓ点が－１９６℃以下の低熱膨張合金を製造することを特徴とする低熱膨張合金の製造方法。 The low thermal expansion alloy material having the composition according to claim 1 or 2 is melted and solidified by a laser or an electron beam to form a laminate, and the average coefficient of thermal expansion at 100 to −70 ° C. is 0 ± 0.2 ppm. A method for producing a low thermal expansion alloy, which comprises producing a low thermal expansion alloy in the range of / ° C. and having an Ms point of -196 ° C. or lower.
  4. 　前記低熱膨張合金素材は、粉末であることを特徴とする請求項３に記載の低熱膨張合金の製造方法。 The method for producing a low thermal expansion alloy according to claim 3, wherein the low thermal expansion alloy material is a powder.
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